Plot

The Returners break the quarantine imposed on Medivac 12 and return to the Fleet, only to spread a virus that has incapacitated a majority of the Fleet's survivors. Meanwhile, terrorist attacks by the Earth Protectorate imperil the Fleet and its search for Earth.

Anastasia falls to the ground, unconscious and sickly-looking. Darrin yells to the Marines to help, unable to help her himself because he is shackled to the table.

Commander Adama notifies the Fleet that they have been hit by a virus, which affects 80% of the people that it comes in contact with. Adama decrees that the virus is the result of the Returners and offers an ultimatum: turn over the Returners or they (and those harboring them) will be hunted down after an hour. Adama vows that after that, said Returners and those harboring them will be hunted down and exterminated, like criminals and traitors.

A member of the Earth Protectorate burns through Galactica's hull and hoists in a Returner: Zak Adama. In exchange for payment from a group of Returner worshippers, the terrorist hands Zak over to them. The leader of this group of robed people tells Zak that they are lead by a dying leader and to prepare himself for what is to come. They rapidly succumb to the virus.

A highly concerned Zak summons help. It comes in the form of Lee Adama, who berates Zak, telling him to get away from the dying people. Zak is happy to see his brother, in return Lee aims his gun at Zak, calling him a Cylon.

From Colonial One, Laura Roslin talks to Commander Adama. Adama informs her that more than 80% of his crew and pilots are infected with the virus. He tells her that if the Cylons should attack, she and other uninfected and functioning ships will have to jump.

Roslin asks after Zak. Adama replies that Lee has "the Cylon" and that he'll be interrogated, studied and then exterminated. She interrupts him, informing him that 10,000 people haven't been infected with the virus. She then asks if Adama remembers sand cats. He replies that he does, commenting that they were beautiful animals, and the conversation ends.

Adama tells Colonel Tigh about the sand cats. Adama relates to the fact that because there were so few sand cats that repopulated the species out of extinction levels, they all died out when they were infested with lung parasites; conversely, these same parasites infected only 5% of the tree lion population. He compares this to the human race's predicament and the need for more people in order to increase their chances of survival as a species. Tigh scoffs this, saying that Roslin's "more of an idiot than I thought".

Commander Adama watches Lee interrogate Zak. During the interrogation, the discussion gets heated. Zak tells Lee about an event on his graduation day, namely after Zak called his father "dad", which resulted in the elder Adama telling Zak that he was a disgrace. Zak then asks what they'll do with him, saying that it would be a relief to die since "this nightmare of being your brother... and his son... would finally be over".

On Medivac 12, Kara Thrace is gun-ho about returning to Galactica. Adama denies her request and tells her to babysit the ship, as Gaius Baltar is en route to comb through the medical records and tissue samples in order to find a cure for the virus. They discuss Zak's death again. Thrace believes that Zak's reappearance is like a second chance, however Adama disagrees.

Baltar's Raptor docks on Medivac 12. Baltar, wearing a complete bio-hazard suit, is greeted by Thrace. Baltar notes that she has not yet been afflicted by the virus, which leads to exchanging barbs. He removes a sample of Zak's hair from her uniform, noting that he had always assumed that she preferred Lee Adama. After she replies that she would take either Adama over Baltar, he tells her to run along for "the grownups have some tests to run".

During the interrogation, Lee reveals that he has feelings for Kara. In response, Zak assaults Lee, ripping off his face mask. As the two Marines come in to remove Zak, a member of the Earth Protectorate makes his bid to kill Lee. This is thwarted by Zak, and finished by the Marines who assault the terrorist into unconsciousness or death.

Lee calls the CIC, who informs him that the terrorists are trying to take out the pilots, and have reports of two groups in his sector. Lee then orders the Marines to go after one group, while he'll dispatch the other; the Marines point out that it would be safer to stick together an take out the terrorists one-by-one. Lee replies that there is no time for that kind of sweep, but Zak offers to help. Much to his chagrin, and against his better judgment, Lee gives Zak a gun.

After dealing with a group of terrorists, Lee succumbs to the virus.

Later, Lee is brought to sickbay. While here, Commander Adama throws Zak against a wall and calls Zak a monster; Lee weakly attempts to stop the attack, saying that Zak saved his life. Before Adama could continue, the ship's lighting dies out.

Adama reports to CIC with Zak, discovering that Gaeta has fallen ill as well. This is not the only event to transpire, as a first-generation basestar jumps in the debris field. Gaeta reports that he's brought Galactica to reserve power in order to avoid detection on the Cylon's DRADIS. Adama assesses the situation, determining that they have a chance, however there are only three active pilots in the Fleet: Thrace, Adama... and Zak.

Analysis

In keeping with the scientific laws pertaining to conservation of energy, even if Galactica diminished its power output, it would still be detectable by DRADIS. This is because the energy generated from the power-plants would have to go somewhere.

Notes

Barring any "in comic" deaths or births, the Fleet's population is 47,850, counting the three possible "in comic" deaths of the Earth Protectorate terrorists shot by Lee and Zak Adama.

The Returners do not impact the survival count.

Roughly 10,000 humans remain uninfected by the Returner virus, which is about 21% of the survivors.

In the Re-imagined Series' canon, the first-generation "antebellum" basestar makes its appearance in "Razor". Before that, the ship was only seen as a model in the Miniseries as an exhibit in the Galactica Museum.

Questions

How did Gaeta succumb to the virus, even with his breathing mask on?

How do the Earth Protectorate's ships manage to breach Galactica's hull without being detected?

Did the other ships power down after the Cylon basestar was detected? (Answer)